Older sealing rings known as buffer seals used for forming a sealed condition around a rod, shaft or other member axially movable in a bore of a hydraulic cylinder include urethane rings having rectangular or near rectangular cross-sectional shapes for providing a bi-directional sealing capability. However, these older bi-directional sealing rings have been found to have a tendency to trap hydraulic fluid or oil between themselves and adjacent sealing rings. This has been problematic because, at times, the trapped fluid or oil rose to a pressure sufficient to damage both the sealing ring and the adjacent seals.
Newer rod sealing ring constructions having a unidirectional sealing capability are also known, including multiple piece sealing rings having a stepped rigid PTFE sealing ring in combination with a more flexible elastomeric backing ring made from an elastomeric material such as rubber. Such unidirectional sealing rings reduce the occurrence of trapped oil between the buffer sealing ring and adjacent rings. However, the backing rings, in some instances, have been found to have a tendency to become permanently deformed under high pressure operating conditions. Additionally, these rings are significantly more expensive than the older bi-directional sealing rings.
Reference various rod and buffer sealing ring constructions and analogous sealing ring constructions disclosed in the following U.S. patents: Jamrus, U.S. Pat. No. 4,323,427, issued Apr. 6, 1982; Kashiwamura et al., U.S. Pat. No. 4,623,151, issued Nov. 18, 1986; Sugahara, U.S. Pat. No. 4,907,495, issued Mar. 13, 1990; Peppiatt et al., U.S. Pat. No. 5,088,745, issued Feb. 18, 1992; and Yamatani, U.S. Pat. No. 4,472,111, issued Sep. 18, 1984.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.